1. Field of the Invention
The present invention is related to restoration of a computer system from backup, and more particularly, to a rapid restoration of a server from an image stored on a network server. The present invention is also related to rapid restoration of local hard drives from a network, or from the Internet.
2. Related Art
With the popularity and success of the Internet, server technologies are of great commercial importance today. An individual server application typically executes on a single physical host computer, servicing client requests.
In conventional systems, the data of the server is typically backed up on some storage device in the form of backup files. If the server crashes or fails, or the software becomes corrupted, it may become necessary to restore the state of the server to some previously backed-up state. The process consists of three steps: (1) the machine is usually physically shut down; (2) the data is copied from the backup storage to the storage, e.g., disk drive, used by the server. During this operation, a dedicated boot procedure can be used (for example, boot from a floppy disk or CD ROM); and (3) the server is restarted.
During the restart time, the server does not perform any useful functions. Also, the process of restoring all the files of the server is time consuming. In corporate networks, a typical server can have 100 Gigabytes (or, frequently, much more than that) of data. With a transfer rate up to 100 Megabytes per second over a network, it would take approximately 1,000 seconds to transfer all the data from the backup storage to the server's local storage. This assumes that the entire network bandwidth is available for this process. Frequently, this is not the case, since only a fraction of the bandwidth may actually be available at any given time for restoring the files from backup. In practice, such transfers of data from backup to the server can take many hours.
Also, even 1,000 seconds of downtime is an extremely long time, particularly for many mission-critical applications. For example, if the server in question is a web server that handles customer requests or sales, a period of 16-20 minutes of downtime can result in substantial lost sales. Furthermore, it is generally believed that for many e-commerce applications, the consumer attention span is relatively short, and a customer who does not receive a rapid response from a web server will simply go to a competitor's website. In other words, there is a need in the art to minimize server downtime during backup, avoid network overloading during the restoration process, and to provide a mechanism to rapidly recover a server after a failure or shutdown.